International Affairs is a leading journal of international relations. Members of Chatham House have access to current and previous issues.

Non-Chatham House members can subscribe via Wiley-Blackwell. Electronic access to the full text of the article via the source url above is only available if you (or the network by which you access ESO) already subscribes to Wiley-Blackwell and your network uses a link resolver.The enlargements of the post-Cold War era have undermined NATO's stated objectives vis-à-vis the purpose of incorporating new members and exposed tensions within the alliance over the twin pillars of the 1967 Harmel Report, namely deterrence and dialogue. NATO's stance on enlargement has not only undermined Euro-Atlantic security and triggered new divisions between East and West, it has also exposed aspirant states, particularly those in the post-Soviet space, to sustained pressure and coercion from Moscow.

This article examines the rationale for NATO enlargement in the post-Cold War era, focusing on the two post-Soviet aspirant states, Georgia and Ukraine. While these two states contribute, as partners, to the alliance's efforts to advance cooperative security, the issue of their prospective membership threatens to undermine alliance security and cohesion, and their ambitions are therefore unlikely to be realized in the foreseeable future. With Russia taking an increasingly assertive stance on the global stage and uncertainty surrounding the direction of US foreign policy under the presidency of Donald Trump, the issue of NATO enlargement is unlikely to be a priority for the alliance over the next few years. If NATO ultimately rejects any prospect of membership for states in the post-Soviet space, they could be abandoned to Russian influence, indicating that Moscow has a de facto veto over membership of the alliance and conceding spheres of influence to Russia.